What is it called when magnetic flux from one coil induces an EMF in a second coil?

When magnetic flux from one coil induces an electromotive force (EMF) in a second coil, this process is known as mutual inductance. Mutual inductance occurs when the change in current flowing through the first coil creates a changing magnetic field that passes through the second coil. According to Faraday's law of electromagnetic induction, this changing magnetic field generates an EMF in the second coil as a result of the magnetic flux linkage between the two coils.

In practical terms, mutual inductance is crucial in the operation of many electrical devices, such as transformers, where one coil (the primary) influences another coil (the secondary) to transfer energy through magnetic coupling. This principle enables the efficient conversion of voltage levels in power distribution and various electronic circuits.

Self-inductance, on the other hand, refers to the phenomenon where a changing current in a single coil induces an EMF in itself, and inductive reactance is related to the opposition to alternating current due to inductance. Electromagnetic induction is a general term that encompasses both self-inductance and mutual inductance, but the specific scenario described in the question refers to the interaction between two separate coils, making mutual inductance the accurate term.